This invention relates starting of an internal combustion engine and particularly to determining engine position during starting.
Engine position is conventionally determined using crankshaft position information. The crankshaft position information is typically produced using a toothed wheel with a missing tooth, so that an engine control module can determine relative engine position to each cylinder. However, since the crankshaft rotates twice per engine cycle, information for the crankshaft can only locate engine position to one of two possibilities. To determine the unique engine position, additional information is used. Typically, this information is provided from a cylinder identification (CID) signal coupled to a camshaft. Thus, the engine control module can therefore uniquely determine relative engine position to each cylinder.
During conventional engine starting, the engine control module waits to receive the CID signal before commencing sequential fuel injection, since sequential fuel injection requires unique identification of engine position. In other words, since the CID signal is provided only once per 2 revolutions of the engine, it takes a certain amount of time to uniquely determine engine position. Therefore, there is a certain delay time before sequential fuel injection can commence. Such a system is described in U.S. Pat. No. 5,548,995.
The inventor herein has recognized a disadvantage with the above approach. In particular, since it can take as many as 2 engine revolution before sequential fuel injection can commence, increased starting time can occur, which degrades customer satisfaction. Conventional approaches in reducing engine start time require injection of fuel using all fuel injectors, since unique engine position is unknown, and any cylinder may be inducting. The inventor herein has recognized that if engine position can be more quickly determined, it may be possible to reduce the amount of fuel injected into cylinders not currently inducting fuel and air while providing acceptable engine starting times.
An object of the invention herein is to quickly determine engine position during engine starting.
The above object is achieved and disadvantages of prior approaches overcome by a method for determining engine position, the engine having a camshaft and a crankshaft, the method comprising the steps of: determining cylinder identification when a camshaft measurement is received; and determining cylinder identification after a predetermined amount of crankshaft rotation when an operating condition is such that said camshaft measurement is receivable and said camshaft measurement is absent.
Thus, according to the present invention, engine position can be determined using either the absence or presence of the camshaft measurement. In other words, the camshaft measurement can occur in only one of two positions since the camshaft rotates once for every two revolutions of the crankshaft. Therefore, if the camshaft measurement does not appear where it should during an engine start, then engine position can be uniquely determined. Similarly, if the camshaft measurement does appear, then again engine position can be uniquely determined. Using this approach, engine position is found faster when it is the case that if the camshaft measurement does not appear. Further, to eliminate false determination of engine position when the camshaft measurement is absent, operating conditions must be such that said camshaft measurement is receivable.
An advantage of the above aspect of the invention is faster average engine starting time.
Another advantage of the above aspect of the invention is improved customer satisfaction, improved fuel economy, and reduced emissions.